docstring for @time_imports: explain what is shown (it's not cumula…

…tive) (#48248)

Co-authored-by: Ian Butterworth <i.r.butterworth@gmail.com>
(cherry picked from commit eb5f6d6)

stdlib/InteractiveUtils/src/macros.jl

@@ -360,6 +360,8 @@ See also: [`code_native`](@ref), [`@code_llvm`](@ref), [`@code_typed`](@ref) and
 A macro to execute an expression and produce a report of any time spent importing packages and their
 dependencies. Any compilation time will be reported as a percentage, and how much of which was recompilation, if any.
 
+One line is printed per package or package extension. The duration shown is the time to import that package itself, not including the time to load any of its dependencies.
+
 On Julia 1.9+ [package extensions](@ref man-extensions) will show as Parent → Extension.
 
 !!! note